As illustrated in FIG. 12a, a tripod type constant velocity universal joint 51 includes an outer joint member 52, a tripod member 60, and spherical rollers 70. The outer joint member 52 has three track grooves 53 formed at trisected positions in a circumferential direction to extend in an axial direction. Roller guide surfaces 54 are formed on opposed side walls of each track groove 53. The tripod member 60 includes trunnion journals 62 radially projecting from trisected positions on a trunnion barrel 61 in the circumferential direction. The spherical rollers 70 are each fitted in a freely rotatable manner about each trunnion journal 62 through intermediation of a plurality of needle rollers 72. The spherical rollers 70 are received in the track grooves 53 of the outer joint member 52, and an outer spherical surface of each spherical roller 70 is guided by the roller guide surfaces 54 formed on both the side walls of each track groove 53.
A root portion A′ of the above-mentioned trunnion journal 62 is illustrated in FIG. 12b in an enlarged manner. As illustrated in FIG. 12b, the root portion A′ is formed into a rounded surface having a curvature radius Rb, which is continuous with a cylindrical outer peripheral surface 74 serving as an inner raceway surface for the needle roller 72. The root portion A′ is connected to a shoulder surface 61a. An inner washer 78 is interposed between an end portion of the needle roller 72 and the shoulder surface 61a. Movement of the needle roller 72 in the axial direction toward the root portion A′ of the trunnion journal 62 is restricted by contact between a side surface of the inner washer 78 and an end surface of the needle roller 72 (see Patent Document 1).
As illustrated in FIG. 12c, there is also known a tripod type constant velocity universal joint without an inner washer at a root portion A″ of a trunnion journal 62′. In this case, movement of a needle roller 72′ in an axial direction toward the root portion A″ of the trunnion journal 62′ is restricted by contact between a shoulder surface 61a′ formed on a trunnion barrel 61′ and an end surface of the needle roller 72′ (see, for example, Patent Document 2).